1. Field of the Invention
The present invention is directed to an alloy coated product with an Al-Zn-Si base alloy coat including an Al-Zn-Fe-Si alloy layer and a method for making the same.
2. Description of the Prior Art
A zinc coating is generally used to provide corrosion resistance to a ferrous-base material. However, higher corrosion resistance is required to use the ferrous material in severe corrosive environments, e.g., a salt spray area such as a seaside, an area having acid rain. From this point of view, many kinds of Al-Zn alloy coats were developed. The demands of the Al-Zn alloy coats are increasing because the Al-Zn alloy coats has superior corrosion resistance than the Zn coat. Japanese Patent Publication [KOKOKU]No. 63-63626 describes a steel wire coated with an Al-Zn alloy containing 3 to 10 wt % of Al. Suzuki et al. Japanese patent early publication [KOKAI]No. 1-263255 also describes a method of Al-Zn alloy coating, which includes the steps of dipping an article into a molten bath of Zn at a bath temperature in a range of 480.degree. to 560.degree. C. to form an undercoat on the article, and subsequently dipping the undercoat into an alloy molten bath containing at least 1 wt % of Al at a bath temperature in a range of 390.degree. to 460.degree. C. to form an Zn-Al alloy coat on the undercoat. The alloy molten bath preferably includes 0.1 to 10 wt % of Al. In case of an Al content less than 0.1%, the desired effect of Al, which is to greatly enhance corrosion resistance of the alloy coat, is not obtained. On the other hand, when the alloy molten bath includes more than 10 wt % of Al, a typical ferrous metal bath container and the article are harmfully attached by the molten metals of the alloy molten bath. However, when we think about a corrosion protective coat used under more severe corrosive conditions in the future, an alloy coat having superior corrosion resistance as compared with the Zn-Al alloy coat will be requested.